Extraction process



Patented Mar. 8, 1938 2,110,311 EXTRACTION PROCESS Monroe Edward Spaght, Martinez, Calif., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application April 24, 1935, Serial No. 17,929

3 Claims.

This invention relates to a process for extracting mineral hydrocarbon oils which are derived from petroleum crude oils, shale oils, coal oils, etc., with selective solvents, and is particularly con- 5 cerned with a process for improving the color of these oils.

It is known that mineral hydrocarbon oils generally contain several types of hydrocarbons; namely, parafi'inic, naphthenic, aromatic and un- 0 saturated constituents. In addition, other components, such as color producing substances, which may or may not be hydrocarbons, are present in smaller quantities. Of these, the paraffinic constituents are the least reactive, and their viscosity is affected the least by temperature variations. Various processes are knownfor concentrating paraflins or paraffinic constituents to improve the quality of lubricating oils. ample, removal of part of the non-parafllnic hydrocarbons, which lower the viscosity index of lubricating 0ils,-by extracting the oil with a selective solvent of the sulfur dioxide type, such as sulfur dioxide or phenol, whereby non-paraffinic constituents of the oil are preferentially dissolved in the selective solvent, is a known process.

A complete or high degree of decolorization of oils by the use of these selective solvents is, however, generally impossible or possible only by using excessive amounts of the solvent, which results 30 in a very low yield of the parafiinic oil.

I have discovered that coloring matter which naturally occurs in these mineral oils can be readily removed by extracting the oil with anhydrous or very concentrated lower aliphatic acids, either in a single-stage batch or continuous manner, or in a multiple stage or countercurrent manner. Acetic, propionic, butyric, and isobutyric acids have been found to be the most suitable for this purpose, but other liquid aliphatic acids may also 40 be employed. With increasing molecular weight of the acids, their critical solution temperatures \m'th oil decrease thereby, necessitating operation at lower temperatures.

By very concentrated aliphatic acids, I mean 45 acids having a water content of or less. Clay or a similar adsorbent material may be employed in conjunction with the aliphatic acid, if desired.

I may employ any desired acid to oil ratio, de-

pending on the temperature of operation and the 50 quantity of coloring matter which is to be re- For exmoved. I have found that ratios between one part of acid'to four parts of oil and four parts of acid to one part of oil to be effective in most cases, but it is understood that my invention is not limited to this range of ratios.

Low boiling aliphatic acids also have a certain selective solvent power for naphthenic, unsaturated and aromatic components of the oil, and an oil which is treated with these acids will, therefore, be improved in regard to its paraffinicity 10 as Well. However, only a small improvement in the paraifinicity is to be expected by merely treating the oils with aliphatic acids, and I prefer to treat the oils in two steps as follows: The oil is extracted in a known manner with a selective solvent of the sulfur dioxide type, producing a more parafiinic oil which is, however, not sufficiently decolorized; the parafi'lnic raflinate from this extraction then is treated with an aliphatic acid as described below to improve its color. Since the second step causes a certain improvement in the parafiinicity, the first step in such a combination process may be less intensive than if it were not followed by the second step of my process. order of these treatments, treating the oil first with the aliphatic acid and then with a selective solvent of the sulfur dioxide type. In accordance with my invention, an oil residue or distillate which may or may not have received prior treatmerit with sulfuric acid, known selective solvents or other refining agents, is mixed with a desired volume of the aliphatic acid. The volume of the solvent depends upon the quantity of the coloring matter which it is desired to remove. The oil and acid may be mixed at a temperature at which they are completely or substantially miscible, and then chilled to cause the mixture to form two liquid phases. However, I may mix the oil and the acid at the temperature at which the necessary phase separation occurs, and use no subsequent chilling. The mixture may then be allowed to remain quiescent or permitted to flow through a settling tank until there is a substantial separation into two strata. The upper layer will consist of the decolorized oil together with asmall quantity of the acid,.while the lower layer will contain most of the acid, coloring matter removed from the raffinate oil and a small quantity of oil. Alternatively, the mixture may be fed It is possible, moreover, to reverse the directly to a centrifugal separator, or to any suitable separating device.

: The'two layers then are separated by decan-' tation or in a centrifugal separator, and-are treated separately to recover the aliphatic acid. Distillation at ordinary'or at reduced pressure is suitable for this purpose. It is also. possible to water.

separated lower or heavier layer, a further sepseparate the acid from the oil by the additionof Thus, by adding sufficient water to the aration into an oil phase and an aqueous acid phase is efiected.- These phasesrmay be separated by decantation. The aliphatic acid may also be removed from the separated phases by washing them with solvents such as ethyl alcohol, acetone, 1 etc., using methods known to those skilled in the art. 1'

When the oil has ahigh content of, coloring matter it may be desirable to treat the extracted oil with additional quantities of acid. This may v be efiected by a multiple extraction process in which fresh acid is used at each stage. I prefer,: however, to use a countercurrent method of treat 'ing according to. which the aliphatic acid is f caused to flow countercurren'tly to the hydro I carbon oil, either in a multi stage :trealterfcom-c prising a series of agitators, or mixers and phase separating means, or by fl'owing the two liquids countercurrently and in contact through one or. 7 more vertical towers provided with liquid'conr tact means, such as packing, etc. w

My invention is especially applicable to the treatment of oilswhich have been extracted with known solvents and are suitable for use as lubricants, but which do not meet certain color or asphalt content specifications or requirements. Moreover, it is useful in the production of high grade specialty oils or white oils. The preliminary extraction may employ any selective solvent which effects a concentration of the paramnie. components of an oilwithout sufliciently improv: ing the color. For convenience, I 'designate'these' solvents as solvents of the sulfur, dioxide type"; The following are examples of these solventsr: V sulfur dioxide; furfural, quinoline; benzaldehyde,

nitrobenzene, 5p dichloroethyl ether, phenol and benzonitrile.

Many other solvents are; however, also suitable.

My invention will be further understoodyfrom the following specific examples which are understood to be illustrative only. 1

Example I .-Equal parts of a sulfur dioxide ex:

tractedroil and 99.5% acetic acid were'agitated.

the mixture was permitted; to stratifyat a temperature ofs20 C. and then was separated into two portions. The upper layer was distilled to. re move the acid, and a-raflinate'having the pro+ per-ties givenin Table I was obtained.

Table I After a:- Belore extraction traction with acetic acid with acetic acid Gravity, A. P. I 26.2 28.9. Visc. sec. S. U. at F-..- r 59.1 74. -C 2(A.B.'I.M.) 19 (Bay- 1 bolt). Refractive index, 11 20 C 1.4945 1.4840. Unsulfonated residue, by vol..." 74.5 80.0

. "Erample-ilhSeparatc. pbrtions of an oil extracted witthsulfur dioxide and kerosene extract oil having an S. U. viscosity of at 100 F.

" were each treated withan aliphatic acid and with adsorbent clay in the' manner described above in Example I. The'properties of the ramnates are shown-in 5 Table The treatment with aliphatic acids may. be applied to oils witha-wide rangeof viscosities. and it is not to be limited to the specific oils described in the, above examples. my invention may be applied to oils falling within .the visc'osityranges of spindle oil, machine on, cylinder. oils, etc.

,I; claix'njas myinvention: r 1

1. Inathe :process. of. decolorizing lubricating rafllnate obtainedby extracting a viscous mineral For example, 

